This disclosure generally relates to an apparatus for curing and/or removing porogens from dielectric materials, and in particular, to an apparatus for curing and/or removing porogens from low k dielectric materials with ultraviolet radiation in a controlled environment.
As semiconductor and other microelectronic devices progressively decrease in size, the demands placed on device components continue to increase. For example, the prevention of capacitive crosstalk between interconnect lines becomes significantly more important with smaller devices. Capacitive crosstalk is generally a function of both the distance between conductors and the dielectric constant (k) of the material placed in between the conductors. Considerable attention has been focused on electrically isolating the conductors from each other using new insulators having low dielectric constants because although silica (SiO2), which has traditionally been used in such devices because of its relatively low dielectric constant of about 4, met the requirements of earlier (i.e., larger) applications, it will not be adequate for the smaller devices of the future. These low k (i.e., a dielectric constant less than 4) materials are desirable for use, for example, as inter-layer dielectric layers (ILD).
To achieve low dielectric constants, one can either use a material that possesses a low dielectric constant, and/or introduce porosity into the material, which effectively lowers the dielectric constant because the dielectric constant of air is nominally 1. Porosity has been introduced in low k materials through a variety of means. In the case of spin on low k dielectrics, a lowering of the k value can be achieved by using high boiling point solvents, by using templates or by porogen based methods that form pores upon subsequent processing to remove a sacrificial material. However, the integration of porous low-k materials in the manufacture of the semiconductor device, in general, has proven difficult.
The utilization of UV radiation for the curing of low-k dielectric films has recently been discovered to provide enhanced electrical, mechanical and chemical properties of the resulting dielectric material, as compared to other cure methods. In addition, the UV assisted process is capable to effectively remove porogen material, a sacrificial organic substance that is used to generate porous structures. Test results on different low-k materials have shown that the exposure to different wavelength distributions of UV light combined with the appropriate background chemistry and sufficiently high wafer temperatures results in different modifications of the low-k films. In particular, we have found that some wavelength distributions (A) are very effective for porogen removal and enhanced cross-linking of the low-k matrix, while other wavelength distributions (B) contribute to the cross-linking of the low-k matrix without porogen removal. Therefore a number of different low-k cure flow schemes are possible, which may have benefits for the synthesis and integration of porous low-k dielectrics.
No ultraviolet radiation apparatus currently exists that addresses the special problems and concerns associated with curing and/or removing porogens from various dielectric materials. Accordingly, there is a need in the art for an apparatus suitable for processing dielectric materials such as low k materials, oxides, nitrides, premetal dielectrics, barrier layers, and the like for advanced device fabrication.